The former Brentford player, 30, sustained the injury during the Republic of Ireland's 0-0 draw with Montenegro on Wednesday.
And now Rowlands, who suffered a carbon copy of the injury against Derby in January, will be out of action for a substantial period.
"Martin's been to see the specialist and the results of the scan unfortunately revealed that he's sustained another anterior cruciate ligament injury," head physio Paul Hunter told the club's official website.
"Martin's a fighter. I've no doubts he'll come back from this.
"He knows what it takes after going through it last season - his attitude was spot on then and I'm sure it will be the same when his rehabilitation begins in the coming months."